1. Field of the Invention
This invention is in the field of mechanical actuators for traction cables, especially as applied to the control of ergonomic supports in seating, particularly automobile seats.
2. Related Art
Ergonomic supports for seats, such as automobile seats, need to be adjustable. Movement of the internal components of ergonomic supports, such as lumbar supports, is often made by applying traction to a traction cable such as Bowden cable. The ergonomic supports frequently require the application of traction under some tension to overcome a static bias of a component and/or the weight of the seat occupant, in order to bring the moving parts into an ergonomically weight supporting position for the comfort of the passenger.
Traction cables such as Bowden cables are typically comprised of a wire that slides axially through a sleeve. At the lumbar support, the wire will be attached to one portion of a stamped metal or molded plastic pressure surface that is mounted to arch into a supporting position when traction is applied to one or both of its ends. The traction cable sleeve is attached to another portion of the pressure surface, or the mount, to apply the traction. See U.S. Pat. No. 6,254,187, incorporated by reference herein, for examples, of such components. Other components may slide in and out of a channel in a housing, with the sliding being powered by the application of traction through the Bowden cable wire. In such devices, the wire is attached to the moving portion and the sleeve to a housing or mount. See U.S. Pat. No. 6,619,739, incorporated by reference herein, for an example of these components. The present invention may be applied to any moving parts that may be actuated by a traction cable.
The mounting of the traction cable on the components of the ergonomic device require that the Bowden cable sleeve end be fixed to a portion of the ergonomic support and the end of the wire that slides through the sleeve be attached to another portion of the ergonomic support. An actuation device mounted at the other end of the traction cable must be able to apply traction to pull the wire through and from the sleeve and also must be able to hold the wire at a selected position along its axial travel relative to the sleeve, in order to thereby hold the connected ergonomic support in a position selected by the user.
Power actuators typically achieve these necessary functions by holding the sleeve end in a fixed position and attaching the wire end to a moving part in order to draw it from the sleeve. In some actuators the moving part is an axially translating lead screw, see U.S. patent application Ser. No. 10/008,896, incorporated by reference herein. In other actuators the moving part is a pulley having a seat for a wire end bullet. Turning the pulley thereby pulls the wire from the sleeve.
In addition to the necessary functions recited above, there is a variety of traits that are desirable in the marketplace for actuators that apply traction manually. Among these are ease of use and a perception by the user that the components move smoothly.
Planetary gears applied to other applications are known. The equilateral symmetry of the drive train is desirable for its mechanical advantage, which promotes ease of use, and for its smooth application of power.
However, the planetary gear itself would not be capable of holding a selected position against the tension applied to the traction cable by use of the ergonomic support it is used to actuate.
There is a need in the art for a smooth, easy to operate planetary gear mechanical actuator that is capable of holding a selected position. As always, there is a continuing need in the art to produce components that are durable and economical.